There will never be a FF NEX. This was easy to work out by considering that when Sony designed a new fully electronic mount from scratch they made it APS-c-sized. The A-mount is less than ideal for a 135 sensor and the E mount is even smaller.

And as Headofdestiny says how many NEX lenses that only cover an APS-c sensor do Sony have to produce before people realise they are deliberately not making E mount lenses that can be used with a FF sensor?

The FF NEX is conceptual fallacy. People imagine a camera in their head made from separate and incompatible technologies. A FF digital sensor, small, non-retrofocus film-era lenses, a lens mount that will just accommodate a 135 sensor when digital imaging requires more clearance than film...

You could make a FF NEX but the lenses would be A-mount sized (in width if not length), the body would require an expensive and custom Leica-style sensor with adjusted microlenses and would need software correction to combat vignetting. Wideangle lenses would need to be corrected for extreme vignetting, colour shift and would have poor corner sharpness.

The camera would be as large as an A37, would perform relatively poorly and would be expensive.